JPWO2012096342A1 - Lithium secondary battery positive electrode additive and lithium secondary battery positive electrode - Google Patents

Abstract

Provided are a positive electrode additive and a lithium secondary battery positive electrode capable of increasing the output of a lithium secondary battery and maintaining cycle characteristics even during high-speed charge / discharge. In the additive, the hydrogen atom at the 3-position and / or 4-position of the thiophene ring is a perfluoroalkylalkoxy group (f1), a perfluoroalkoxy group (f2), a perfluoroalkoxyalkyl group (f3), and the above (f1). The substituted polythiophene (P) having the repeating unit (D) substituted with at least one group (f) selected from the group consisting of the alkyl group (f4) substituted with at least a part of the thiophene repeating units is essential. It is an additive for a lithium secondary battery positive electrode as a component.

Description

  The present invention relates to an additive for a positive electrode of a lithium secondary battery and a positive electrode material.

  In recent years, in order to meet the needs of electric vehicles, there is an urgent need to increase the output of lithium secondary batteries. In general, there are two important factors for increasing the output of a battery. One is that the electrode material has high electron conductivity, and the other is that lithium ion has high conductivity. When either one is inferior, the internal resistance of the battery becomes high and sufficient output characteristics cannot be obtained. The main cause of the internal resistance is the electrode material where the reaction interface between ion conduction and electron conduction is concentrated.

  In general, a positive electrode material of a lithium secondary battery is configured by binding a current collector and an active material with a binder. As the binder, polyvinylidene fluoride having a strong binding force is used. However, polyvinylidene fluoride does not have electronic conductivity, and a conductive additive is mixed as a countermeasure. However, the conductivity is still insufficient. Moreover, since there is no conductivity of lithium ions, it is an obstacle to high output.

  It has been proposed to use a conductive polymer compound such as polyaniline as a conductive aid for improving the conductivity of the binder (for example, Patent Document 1). However, the electrode material using the polyaniline of Patent Document 1 as a binder has a problem of poor electrochemical stability and insufficient storage stability and cycle characteristics.

  In order to solve this problem, an electrode material using polythiophene having excellent electrochemical stability as a binder has been proposed, and storage stability and cycle characteristics have been improved (for example, Patent Document 2).

JP 2007-52940 A JP 2010-135310 A

However, although the electrode material of Patent Document 2 has improved electrochemical stability, storage stability, and cycle characteristics, there is room for improvement in withstand voltage and cycle characteristics at high temperatures.
The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrode additive and an electrode capable of increasing the output of a lithium secondary battery and maintaining cycle characteristics even during high-speed charge / discharge. To provide materials.

The inventors of the present invention have reached the present invention as a result of studies to achieve the above object.
That is, the present invention is at least selected from the group consisting of groups (f1) to (f4) in which the hydrogen atom at the 3-position and / or 4-position of the thiophene ring is represented by the following general formulas (1) to (4), respectively. An essential component is a substituted polythiophene (P) having a repeating unit (D) of thiophene substituted with one kind of group (f) (hereinafter also referred to as a repeating unit (D)) as at least a part of the thiophene repeating unit. An additive for a lithium secondary battery positive electrode (hereinafter also referred to as an additive (A) for a lithium secondary battery positive electrode, an additive for a positive electrode (A), an additive (A), etc.); and the additive (A ), A positive electrode for a lithium secondary battery comprising the active material (B) and the current collector (C); a lithium secondary battery comprising the additive (A).
—OR ¹ —R ² (1)
In the formula, R ¹ represents an alkylene group having 1 to 6 carbon atoms, and R ² represents a perfluoroalkyl group having 1 to 15 carbon atoms.
—O—R ³ (2)
Wherein, ^{R 3} represents a perfluoroalkyl group having 1 to 15 carbon atoms.
—R ⁴ —O—R ⁵ (3)
In the formula, R ⁴ represents a linear or branched alkylene group having 1 to 6 carbon atoms, and R ⁵ represents a perfluoroalkyl group having 1 to 15 carbon atoms.
—R ⁶ —OR ⁷ —R ⁸ (4)
In the formula, R ⁶ represents a linear or branched alkylene group having 1 to 6 carbon atoms, R ⁷ represents an alkylene group having 1 to 6 carbon atoms, and R ⁸ represents a perfluoroalkyl group having 1 to 15 carbon atoms. Represent.

  The additive for a lithium secondary battery positive electrode of the present invention has the effect of greatly improving the output characteristics of the battery and greatly improving the cycle characteristics during high-speed charge / discharge.

  The additive (A) for a lithium secondary battery positive electrode of the present invention includes groups (f1) to (f1) to (3) in which hydrogen atoms at the 3-position and / or the 4-position of thiophene are represented by the general formulas (1) to (4). A substituted polythiophene (P) having a repeating unit (D) of thiophene substituted with at least one group (f) selected from the group consisting of f4) is an essential component. The elements listed with the symbols (f1), (f2), (f3), and (f4) are referred to as a perfluoroalkylalkoxy group (f1) and a perfluoroalkoxy group, respectively, in the present specification. Also referred to as (f2), a perfluoroalkoxyalkyl group (f3), and an alkyl group (f4) substituted with the perfluoroalkylalkoxy group (f1).

  The additive (A) for a lithium secondary battery positive electrode according to the present invention is a contact point between a conductive additive and an active material by using a substituted polythiophene (P) having both electron conductivity and lithium ion conductivity as an essential component. The electron conduction that has been carried out through can now be carried out throughout the additive.

  In addition, since the positive electrode additive (A) of the present invention has the repeating unit (D), the lithium ion conductivity is improved as compared with the conventional additive, and as a result, the internal resistance and electrical resistance are greatly increased. Thus, the output characteristics can be improved and the cycle characteristics at high potential and high temperature can be improved.

  Examples of the perfluoroalkylalkoxy group (f1) include a perfluoroalkylalkoxy group having an oxyalkylene group having 1 to 6 carbon atoms and one terminal being a perfluoroalkyl group having 1 to 15 carbon atoms.

Examples of R ¹ in the general formula (1) include a methylene group, an ethylene group, a propylene group, an n-, sec-, an iso-butylene group, a pentylene group, a hexylene group, and a 1,4-cyclohexylene group. .

R ² in the general formula (1) is a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluoro-n-, iso-, sec- or tert-butyl group, Fluoropentyl group, perfluorohexyl group, perfluoroheptyl group, perfluorooctyl group, perfluoro-2-ethylhexyl group, perfluorononyl group, perfluorodecyl group, perfluoroundecyl group, perfluorododecyl group, perfluoro Examples include tridecyl group, perfluorotetradecyl group, and perfluoropentadecyl group.

  (F1) is preferably a linear or branched perfluoroalkylethoxy group having 1 to 6 carbon atoms, and more preferably a linear or branched perfluoroalkylethoxy group having 1 to 4 carbon atoms.

  As said perfluoro alkoxy group (f2), a C1-C15 perfluoro alkoxy group is mentioned.

Examples of R ³ in the general formula (2) include the same as those exemplified for R ² .

  (F2) is preferably a linear or branched perfluoroalkoxy group having 1 to 6 carbon atoms, and more preferably a linear or branched perfluoroalkoxy group having 1 to 4 carbon atoms.

  As said perfluoroalkoxyalkyl group (f3), the C1-C6 alkyl group substituted by the C1-C15 perfluoroalkoxy group is mentioned.

R ⁴ in the general formula (3) is methylene group, ethylene group, n- or iso-propylene group, n-, sec-, iso-butylene group, pentylene group, hexylene group and 1,4-cyclohexylene. Groups and the like. Examples of R ⁵ in the general formula (3) include the same as those exemplified for R ² .

What is preferable as (f3) is, as R ⁴ , a linear or branched alkylene group having 1 to 3 carbon atoms, and as R ⁵ , a linear or branched perfluoroalkyl group having 1 to 6 carbon atoms, More preferably, R ⁴ is an alkylene group having 1 or 2 carbon atoms, and R ⁵ is a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms.

The alkylene group (R ⁶ ) in the general formula (4) in the alkyl group (f4) substituted with the perfluoroalkylalkoxy group (f1) of the repeating unit (D) of thiophene has 1 to 6 carbon atoms. An alkylene group is mentioned.

Examples of R ⁶ in the general formula (4) include the same as those exemplified for R ⁴ .
Examples of R ⁷ in the general formula (4) include the same as those exemplified for R ¹ .
As R < ⁸ > in the said General formula (4), the thing similar to what was illustrated by said R < ² > is mentioned.

Preferred as (f4) is that R ⁶ is a linear or branched alkylene group having 1 to 3 carbon atoms, R ⁷ is an ethylene group, and R ⁸ is a linear or branched chain having 1 to 6 carbon atoms. More preferably, R ⁶ is an alkylene group having 1 or 2 carbon atoms, and R ⁸ is a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms.

  The group (f) is preferably (f1) from the viewpoint of battery output characteristics, more preferably 2,2,2-trifluoroethoxy group, 2,2,3,3,3-pentafluoro. Propoxy group, 2,2,3,3,4,4,4-heptafluorobutoxy group, 2,2,3,3,4,4,5,5,5-nonafluoropentoxy group, 3,3, 3-trifluoro-1-propoxy group, 4,4,4-trifluoro-1-butoxy group or 5,5,5-trifluoro-1-pentoxy group.

The substituted polythiophene (P) in the present invention is at least one group selected from the group consisting of a group (h1) represented by the following general formula (10) and a group (h2) represented by the following general formula (11). The repeating unit (F) of thiophene substituted with (h) may be included.
-(OR ⁹ ) _r -OR ¹⁰ (10)
In the formula, r is an integer of 0 to 5. R ⁹ is a linear or branched alkylene group having 2 to 4 carbon atoms, and R ¹⁰ is a linear or branched alkyl group having 1 to 12 carbon atoms.
_{^{-R 11 - (OR 12) s}} -OR 13 (11)
In formula, s is an integer of 0-5. R ¹² is a linear or branched alkylene group having 2 to 4 carbon atoms, and R ¹³ is a linear or branched alkyl group having 1 to 12 carbon atoms. R ¹¹ is a linear or branched alkylene group having 1 to 4 carbon atoms.

OR ⁹ and OR ¹² in the general formula (10) or (11) each independently represent an oxyethylene group, an oxypropylene group, or an oxybutylene group, and an oxyethylene group is preferable from the viewpoint of conductivity.

R ¹⁰ and R ¹³ in the general formula (10) or (11) are, for example, methyl group, n- or iso-propyl group, n-, iso-, sec- or tert-butyl group, n- or iso- Pentyl group, cyclopentyl group, n- or iso-hexyl group, cyclohexyl group, n- or iso-heptyl group, n- or iso-octyl group, 2-ethylhexyl group, n- or iso-nonyl group, n- or iso -Represents a decyl group, an n- or iso-undecyl group and an n- or iso-dodecyl group.

In the general formula (10), when r is 1 or more, R ¹⁰ is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, from the viewpoint of conductivity. A linear or branched alkyl group. When r is 0, R ¹⁰ is preferably a linear or branched alkyl group having 3 to 12 carbon atoms, more preferably a linear or branched alkyl group having 6 to 12 carbon atoms, from the viewpoint of conductivity. It is.

In the general formula (11), when s is 1 or more, R ¹³ is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, from the viewpoint of conductivity. A linear or branched alkyl group. When s is 0, R ¹³ is preferably a linear or branched alkyl group having 3 to 12 carbon atoms, more preferably a linear or branched alkyl group having 6 to 12 carbon atoms, from the viewpoint of conductivity. It is.

R ¹¹ in the general formula (11) represents, for example, a methylene group, 1,2- or 1,3-propylene group and 1,2-, 1,3-, 2,3- or 1,4-butylene group. In view of solvent solubility and conductivity, a linear or branched alkylene group having 1 to 3 carbon atoms is preferable, and an alkylene group having 1 or 2 carbon atoms is more preferable.

  R and s in the said General formula (10) or General formula (11) are the integers of 0-5 each independently. r is preferably 1 to 5 and more preferably 2 to 5 from the viewpoints of solvent solubility and conductivity. From the viewpoint of solvent solubility and conductivity, s is preferably 0 to 4, and more preferably 0 to 3.

  The content of the repeating unit (D) of the thiophene in the substituted polythiophene (P) is preferably 30 to 100 mol%, more preferably 35 to 100 mol%, particularly preferably 40 to 100, from the viewpoint of solvent solubility. Mol%.

  The content of the repeating unit (F) of the thiophene substituted with the group (h) in the substituted polythiophene (P) is preferably 0 to 50 mol%, more preferably from the viewpoint of withstand voltage and high temperature cycle characteristics. Is 10 to 40 mol%, particularly preferably 10 to 30 mol%.

  The substituted polythiophene (P) in the present invention may contain an unsubstituted thiophene repeating unit.

  As the repeating unit (D) of thiophene, a group bonded to the 3-position and 4-position of the thiophene ring is a combination of a hydrogen atom and a group (f), a combination of different groups (f) or a group (f) Combination with group (h).

  The thiophene repeating unit (D) is preferably a thiophene repeating unit (D1) represented by the following general formula (5) or a thiophene represented by the general formula (6) from the viewpoint of conductivity and solvent solubility. A repeating unit (D2) of formula (7), a repeating unit (D3) of thiophene represented by formula (7), and a repeating unit (D4) of thiophene represented by formula (8). Let (P1) be a substituted polythiophene having as a repeating unit at least one selected from the group consisting of (D1) to (D4). Preferred as (P1) is from 50 to 100 mol%, more preferably 60 to 100 mol%, particularly preferably 70 to 100 mol% of (D1) or (D4) from the viewpoint of solvent solubility and ease of synthesis. % Content.

  The substituted polythiophene (P) in the present invention can be synthesized by a known method such as anionic polymerization or oxidation polymerization of a monomer corresponding to each thiophene repeating unit. Hereinafter, these monomers for synthesis will be described.

  Examples of the monomer corresponding to the substituted thiophene repeating unit (D) include a perfluoroalkylalkoxy group (f1), a perfluoroalkoxy group (f2), and a perfluoroalkoxyalkyl group at the 3-position and / or 4-position of the thiophene ring. (F3), or a thiophene substituted with the alkyl group (f4) substituted with the perfluoroalkylalkoxy group (f1) and substituted with a halogen atom at the 2- and 5-positions.

  Specific examples of the monomer in which the 3-position of the thiophene ring is substituted with a perfluoroalkylalkoxy group (f1) include thiophene in which the 2-position and 5-position of the following thiophene (d1) are substituted with a halogen atom. As thiophene (d1), 3- (3,3,4,4,5,5,6,6,6-nonafluoro-1-hexyloxy) thiophene, 3- (3,3,4,4,5, 5,6,6,7,7,8,8,8-tridecafluoro-1-octyloxy) thiophene, 3- (3,3,4,4,5,5,6,6,7,7, 8,8,9,9,10,10,10-heptadecafluoro-1-decyloxy) thiophene, 3- (4,4,5,5,5-pentafluoro-1-pentyloxy) thiophene, 3- ( 4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene, 3- (4,4,5,5,6,6,7,7,8,8, 9,9,9-tridecafluoro-1-nonyloxy) thiophene or 3- (4,4,5,5,6,6,7,7,8, , 9,9,10,10,11,11,11- heptadecafluoro-1-undecyloxy) thiophene and the like.

  Specific examples of the monomer in which the 3-position of the thiophene ring is substituted with a perfluoroalkoxy group (f2) include thiophene in which the 2-position and 5-position of the following thiophene (d2) are substituted with a halogen atom. As thiophene (d2), 3-perfluoromethoxythiophene, 3-perfluoroethoxythiophene, 3-perfluoropropoxythiophene, 3-perfluorobutoxythiophene, 3-perfluoropentyloxythiophene, 3-perfluorohexyloxythiophene , 3-perfluoroheptyloxythiophene, 3-perfluorooctyloxythiophene, 3-perfluorononyloxythiophene, 3-perfluorodecyloxythiophene, 3-perfluoroundecyloxythiophene, 3-perfluorododecyloxythiophene, etc. Is mentioned.

  Specific examples of the monomer substituted with the perfluoroalkoxyalkyl group (f3) include thiophene in which the 2-position and 5-position of the following thiophene (d3) are substituted with a halogen atom. Examples of thiophene (d3) include 3-perfluoromethoxymethylthiophene, 3-perfluoroethoxymethylthiophene, 3-perfluoropropoxymethylthiophene, 3-perfluorobutoxymethylthiophene, 3-perfluoropentyloxymethylthiophene, 3- Perfluorohexyloxymethylthiophene, 3-perfluoroheptyloxymethylthiophene, 3-perfluorooctyloxymethylthiophene, 3-perfluorononyloxymethylthiophene, 3-perfluorodecyloxymethylthiophene, 3-perfluoroundecyloxy Methylthiophene, 3-perfluorododecyloxymethylthiophene, 3-perfluorotridecyloxymethylthiophene, 3-perfluorotetradecyloxime Ruthiophene, 3-perfluoropentadecyloxymethylthiophene, 3- (2-perfluorohexyloxyethyl) thiophene, 3- (3-perfluorohexyloxypropyl) thiophene and 3- (4-perfluoroheptyloxybutyl) Examples include thiophene.

  Specific examples of the monomer substituted with the alkyl group (f4) substituted with the perfluoroalkylalkoxy group (f1) include the following thiophene substituted with a halogen atom at the 2-position and 5-position of the thiophene (d4): Can be mentioned. Thiophene (d4) includes 3- (4,4,5,5,5-pentafluoro-2-oxapentyl) thiophene, 3- (4,4,5,5,6,6,6-heptafluoro- 2-oxahexyl) thiophene, 3- (5,5,6,6,7,7,8,8,8-nonafluoro-2-oxaoctyl) thiophene, 3- (5,5,6,6,7, 7,8,8,9,9,10,10,10-tridecafluoro-2-oxadecyl) thiophene and 3- (5,5,6,6,7,7,8,8,9,9,10) , 10, 11, 11, 12, 12, 12-heptadecafluoro-2-oxadodecyl) thiophene and the like.

  Specific examples of the monomer in which the 3rd and 4th positions of the thiophene ring are substituted with the group (f) include the following thiophenes in which the 2nd and 5th positions of the following thiophene (d5) are substituted with halogen atoms. As thiophene (d5), 3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) -4-perfluoroethoxythiophene, 3-perfluoroethoxymethyl- 4- (4,4,5,5,5-pentafluoro-2-oxapentyl) thiophene, 3- (4,4,5,5,6,6,7,7,8,8,9,9, 9-tridecafluoro-1-nonyloxy) -4- (5,5,6,6,7,7,8,8,9,9,10,10,10-tridecafluoro-2-oxadecyl) thiophene, etc. Is mentioned.

  Examples of the monomer corresponding to the unsubstituted thiophene repeating unit include thiophenes in which the 2-position and 5-position are substituted with halogen atoms.

  Monomers corresponding to the repeating unit (F) of thiophene substituted with the group (h) include 3-hexyloxythiophene, 3- (2,5-dioxaheptyl) thiophene, 3- (1,3-dioxo Pentyl) -4-methoxythiophene and the like substituted with a halogen atom at the 2-position and 5-position.

  The stereoregularity (RR) of the substituted polythiophene (P) in the present invention is usually 50% or more, preferably 80% or more, more preferably 90% or more from the viewpoint of conductivity. RR is based on the substituent (f), and the groups bonded to the 3-position and 4-position of the thiophene ring of the substituted polythiophene (P) are different from each other in combination of the hydrogen atom and the group (f). This is applied to a combination of groups (f), a combination of groups (f) and (h), or a combination of groups (f) and groups (g) described later.

The definition of stereoregularity (RR) in the present invention will be described below.
As a typical example of the bond of the substituted polythiophene (P), as shown in the following general formula representing a combination of a hydrogen atom and a group (f), an HT-HT bond (B1), a TT-HT bond (B2), There are four types: HT-HH bond (B3) and TT-HH bond (B4). Here, HT is an abbreviation for head to tail, TT is an abbreviation for tail to tail, and HH is an abbreviation for head to head.

  R in the chemical formulas of the above four bond types is substituted with a perfluoroalkylalkoxy group (f1), a perfluoroalkoxy group (f2), a perfluoroalkoxyalkyl group (f3), and the perfluoroalkylalkoxy group (f1). Represents an alkyl group (f4).

The stereoregularity (RR) in the present invention is defined by the ratio (%) of HT-HT bonds (head-to-tail-head-to-tail bonds) in the substituted polythiophene (P), and is calculated by the following formula (1). .
Stereoregularity (RR) = b1 × 100 / (b1 + b2 + b3 + b4) Formula (1)
Where b1: HT-HT bond number, b2: TT-HT bond number, b3: HT-HH bond number, b4: TT-HH bond number.

Specifically, the protons possessed by these bonds each show a specific chemical shift (δ) by nuclear magnetic resonance ( ¹ H-NMR), and are calculated from the integrated values of chemical shifts corresponding to the four types of bonds. can do. In the case of the substituted polythiophene having the thiophene repeating unit (D1) represented by the general formula (5), specifically, B1: δ = 6.98, B2: δ = 7.00, B3: δ = 7. 02, B4: δ = 7.05. Therefore, the integral values S1, S2, S3, S4 in the chemical shifts unique to B1, B2, B3, B4 are calculated, and the stereoregulation rule is calculated from the ratio (%) of the integral value S1 in the chemical shift unique to B1 to the sum of the integral values. The property (RR) is calculated using the following mathematical formula (2).
Stereoregularity (RR) = S1 × 100 / (S1 + S2 + S3 + S4) Formula (2)

  As described above, the substituted polythiophene (P) becomes solvent-soluble by having the repeating unit (D1), (D2), (D3) or (D4) of thiophene, but one or more of (P) By further introducing a sulfonium group (g) represented by the following general formula (9) into the thiophene repeating unit, the affinity with water is increased, and a water-dispersible substituted polythiophene (P2) can be obtained. . Preferred as such a substituted polythiophene is a repeating unit of at least one thiophene selected from the group consisting of repeating units (E1) to (E4) of thiophene represented by the following general formulas (12) to (15) ( E) and substituted polythiophene (P2) having a repeating unit (D).

-SO ₃ ^- M ⁺ (9)
In the formula, M ⁺ is an alkali metal cation or a proton.

M ⁺ in the general formula (9) represents an alkali metal cation (such as a lithium cation ion, a sodium ion, or a potassium ion) or a proton. M ⁺ is preferably an alkali metal cation from the viewpoint of dispersibility in water, and more preferably lithium ion from the viewpoint of stability to the electrolyte.

  The substituted polythiophene (P2) having the thiophene repeating unit (D) and the thiophene repeating unit (E) can be produced by sulfonating the substituted polythiophene (P1) with a sulfonation reagent. Examples of the sulfonation reagent include, but are not limited to, monochlorosulfuric acid, fuming sulfuric acid, and concentrated sulfuric acid.

  The content of the repeating unit (E) of thiophene in the substituted polythiophene (P2) is usually from 5 to 70 mol%, preferably from 30 to 60 mol%, from the viewpoints of water dispersibility, conductivity and ease of synthesis. More preferably, it is 50-60 mol%.

  The content of the repeating unit (D) of thiophene in the substituted polythiophene (P2) is usually 30 to 95 mol%, preferably 40 to 70 mol%, from the viewpoint of water dispersibility, conductivity, and ease of synthesis. Preferably it is 40-50 mol%.

  As the substituted polythiophene (P) in the present invention, the substituted polythiophene (P1) is preferable from the viewpoint of conductivity, and the substituted polythiophene (P2) is preferable from the viewpoint of environmental load that does not use an organic solvent.

  The additive (A) in the present invention may be mixed with a polymer compound or a conductive aid that assists the binding force as necessary. When using a polymer compound that assists the binding force when the substituted polythiophene (P) is dissolved in an organic solvent to be described later, a polymer compound that is soluble in the organic solvent can be mixed. When polythiophene (P) is used by dispersing in water, a water-soluble polymer compound can be mixed.

  Examples of the polymer compound soluble in the organic solvent include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride, tetrafluoroethylene-hexafluoroethylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer. (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chloroto Fluoroethylene copolymer (ECTFE), vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene copolymer and vinylidene fluoride - perfluoromethylvinylether - can be exemplified tetrafluoroethylene copolymer. Among these, polyvinylidene fluoride and polytetrafluoroethylene (PTFE) are particularly preferable from the viewpoint of dispersibility of the substituted polythiophene (P) in the present invention in the polymer compound.

  Examples of the water-soluble polymer compound include cellulose derivatives, poly (meth) acrylic acids, polyvinyl alcohol, polyvinyl sulfonic acid, polyvinylidene fluoride, polyvinyl pyrrolidone, polyethylene oxide, polyacrylamide, poly-N-isopropylacrylamide, poly- N, N-dimethylacrylamide, polyoxyethylene, polyethyleneimine and the like can be mentioned.

In particular, cellulose derivatives include carboxymethyl cellulose (including Li salt, Na salt, K salt or NH ₄ salt), methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, cellulose acetate butyrate, oxidized starch and phosphorylated starch.

Poly (meth) acrylic acids include (meth) acrylic acid homopolymers, copolymers of (meth) acrylic acid and itaconic acid and / or maleic acid, and their Li salts, Na salts, K Salt or NH ₄ salt.

  Among these, preferred are cellulose derivatives, more preferred are carboxymethylcellulose, and particularly preferred are carboxymethylcellulose salts.

  Content of the high molecular compound which assists the binding force in an additive (A) is 0 to 80 weight% normally, Preferably it is 1 to 50 weight%. If the content of the polymer compound is too large, the output is reduced, which is not preferable.

  The conductive auxiliary agent that can be mixed with the additive (A) of the present invention is not particularly limited as long as it is an electron conductive material that does not cause a chemical change at the charge / discharge potential of the positive electrode material used. Examples of the conductive assistant include graphites such as natural graphite (flaky graphite etc.) and artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, carbon nanotubes, and the like. , Conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride, copper, nickel, aluminum and silver, conductive whiskers such as zinc oxide and potassium titanate, conductive metals such as titanium oxide Examples thereof include organic conductive materials such as oxides and polyphenylene derivatives, and mixtures thereof. Of these conductive agents, artificial graphite, acetylene black and nickel powder are particularly preferred.

  Although content of the conductive support agent in an additive (A) is not specifically limited, 1 to 50 weight% is preferable, More preferably, it is 1 to 30 weight%. In the case of carbon or graphite, 2 to 15% by weight is particularly preferable.

  The positive electrode for a lithium secondary battery of the present invention contains an additive (A), an active material (B), and a current collector (C).

  The positive electrode for a lithium secondary battery of the present invention is obtained by kneading an additive (A), an active material (B), and a solvent, and then applying the kneaded material to a current collector (C) and drying it. Can do.

  Specifically, the additive (A) and the active material (B) are mixed in a desired ratio, and a solvent is added thereto to obtain a slurry-like kneaded product. The obtained kneaded material is applied to a current collector (C) such as an aluminum foil and dried, and further pressed at a predetermined pressure as necessary to obtain an electrode. In addition, it is preferable that the drying temperature at the time of drying a kneaded material shall be 100-150 degreeC, and it is still more preferable to set it as 120-140 degreeC. When the drying temperature is less than 100 ° C., the amount of the solvent remaining in the electrode material may increase, which may adversely affect the characteristics of the battery. On the other hand, when the temperature exceeds 150 ° C., the additive (A) is likely to be decomposed (carbonized), which may adversely affect the characteristics of the battery.

As the active material (B), a lithium transition metal composite oxide can be used. For example, Li _x FePO ₄ , Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _y Ni _1-y. O ₂ , Li _x Co _y M _1-y O _z , Li _x Ni _{1- y My} O _z , Li _x Mn ₂ O ₄ , Li _x Mn _{2- y My} O ₄ (where M is Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb and B. At least one atom selected from x, x is a number from 0 to 1.2, y is 0 to 0 0.9, and z is a number from 2.0 to 2.3). Here, the value of x described above is a value before the start of charge / discharge, and increases or decreases due to charge / discharge. Among these, preferably _Li x FePO _4, or _Li x CoO ₂ in terms of cost, further _Li x FePO ₄ are preferable in view of safety of not exothermic decomposition even at a high temperature of over 160 degrees.

  The amount of the additive (A) relative to the active material (B) in the present invention is usually 1 to 20% by weight. Preferably it is 3 to 10 weight%, More preferably, it is 3 to 5 weight%. If the amount of the binder is too small, the active material cannot be sufficiently bonded, and if the amount is too large, the energy density of the battery is lowered, which is not preferable.

  The solvent for kneading the additive (A) and the active material (B) of the present invention has a boiling point of 150 when the substituted polythiophene (P) contained in the additive (A) is a substituted polythiophene (P1). An organic solvent having a temperature of less than 0 ° C. is preferred.

  The organic solvent preferably has a boiling point of less than 150 ° C. If the boiling point is 150 ° C. or higher, the amount of the solvent remaining in the electrode material in the drying process may increase, which may adversely affect the battery characteristics. Examples of such an organic solvent include 1-methyl-2-pyrrolidone, dimethylformamide, chloroform, tetrahydrofuran (hereinafter abbreviated as THF), 1,3-dioxolane, 1,4-dioxane, toluene and the like. Among these, 1-methyl-2-pyrrolidone and 1,3-dioxolane are preferable from the viewpoint of solubility of the substituted polythiophene (P).

  The amount of the solvent when producing the positive electrode of the present invention is 50 to 300% by weight, preferably 50 to 100% by weight, based on the active material (B). If the amount of the solvent is too small, the active material (B) and the additive (A) cannot be sufficiently kneaded. If the amount is too large, the amount of the solvent remaining in the electrode material may increase, which adversely affects the battery characteristics. Since it may affect, it is not preferable.

  The current collector (C) used in the present invention is not particularly limited as long as it is an electronic conductor that does not cause a chemical change at the charge / discharge potential of the positive electrode used. For example, the material is stainless steel, aluminum, titanium, carbon. In addition to the conductive resin and the like, an alloy or the like obtained by treating carbon or titanium on the surface of aluminum or stainless steel is used. Of these, aluminum and aluminum alloys are particularly preferable. These materials can be used by oxidizing the surface thereof. Further, it is desirable to make the current collector surface uneven by surface treatment.

Examples of the shape of the current collector (C) include foils, films, sheets, nets, punched ones, lath bodies, porous bodies, foams, fiber groups, and nonwoven fabric shaped bodies.
The thickness of the current collector is not particularly limited, but is preferably 1 to 500 μm.

  By using such a positive electrode, the lithium secondary battery of the present invention can be obtained.

  Hereinafter, although an example and a comparative example explain the present invention further, the present invention is not limited to these. Hereinafter, a part shows a weight part.

<Production Example 1>
Synthesis of poly {3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene} (P1-1):
(1) Synthesis of 3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene;
2.41 parts of sodium hydride (60% paraffin dispersion) is dispersed in 7 parts of N, N-dimethylformamide, and 3,3,4,4,5,5,6,6,6-nonafluoro-1- 15.92 parts of hexanol [manufactured by Aldrich] was added dropwise. The reaction solution foamed and became cloudy. When the foaming stopped, 4.91 parts of 3-bromothiophene (manufactured by Aldrich) and 0.115 part of copper (I) iodide were sequentially added to the reaction solution.
The reaction solution was heated to 110 ° C. and reacted for 2 hours. After completion of the reaction, the mixture was allowed to cool to room temperature, 30 parts of 1M aqueous ammonium chloride solution was added, and the mixture was transferred to a separatory funnel using 30 parts of ethyl acetate, and then the aqueous layer was separated. Further, the organic layer was washed twice with 30 parts of distilled water, and then ethyl acetate was distilled off to give 3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy). 9.39 parts (90% yield) of thiophene were obtained.

(2) Synthesis of 2,5-dibromo-3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene;
9.39 parts of 3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene and 9.90 parts of N-bromosuccinimide in 30 parts of THF It was dissolved and reacted at room temperature for 2 hours.
The precipitate was removed with a glass filter using 50 parts of ethyl acetate, and THF and ethyl acetate were distilled off. The resulting mixture was purified on a silica gel column to give 2,5-dibromo-3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene 10.80. Part (yield 79%) was obtained.

(3) Synthesis of poly {3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene} (P1-1);
After dissolving 10.80 parts of the above 2,5-dibromo-3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene in 30 parts of THF, methyl Magnesium bromide in THF (21.21 parts) was added and reacted at 75 ° C. for 30 minutes. To the reaction solution, 0.116 part of [1,3-bis (diphenylphosphino) propane] -dichloronickel (II) was added, and the mixture was further reacted at 75 ° C. for 2 hours.
The reaction solution was allowed to cool to room temperature, and 5 parts of methanol was added. The reaction mixture was transferred to a Soxhlet extractor and washed sequentially with 150 parts of methanol, 150 parts of chloroform and 150 parts of acetone. Finally, the residue is extracted with 150 parts of 1-methyl-2-pyrrolidone, and the solvent is distilled off to remove poly {3- (4,4,5,5,6,6,7,7,7-nonafluoro-1 -Heptyloxy) thiophene} (P1-1) 2.95 parts (yield 40%, total yield 28%). The stereoregularity calculated by the aforementioned method using ¹ H-NMR was 96.3%.

<Production Example 2>
Synthesis of poly {3- (4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-1-nonyloxy) thiophene} (P1-2):
3,3,4,4,5,5,6,6,6-nonafluoro-1-hexanol instead of 15.92 parts 3,3,4,4,5,5,6,6,7,7, The polyregularity is 95.6% in the same manner as in Production Example 1 except that 20.23 parts of 8,8,8-tridecafluoro-1-octanol (manufactured by Tokyo Chemical Industry Co., Ltd.) is used. {3- (4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-1-nonyloxy) thiophene} (P1-2) 3.05 parts Obtained (overall yield 25%).
In addition, 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexanol is changed to 3,3,4,4,5,5,6,6,7,7,8,8, When changing to 8-tridecafluoro-1-octanol, the amount of each raw material was adjusted so that the molar ratio of the reaction components and the weight ratio of the non-reaction components (solvent, etc.) were the same as in Production Example 1. And operated. It carried out similarly about the following manufacture examples 3, 5-7, and 9-11.

<Production Example 3>
Poly {3- (4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoro-1-undecyloxy) thiophene } Synthesis of (P1-3):
3,3,4,4,5,5,6,6,6-nonafluoro-1-hexanol instead of 15.92 parts 3,3,4,4,5,5,6,6,7,7, Stereoregularity in the same manner as in Production Example 1 except that 23,55 parts of 8,8,9,9,10,10,10-heptadecafluoro-1-decanol (manufactured by Tokyo Chemical Industry Co., Ltd.) was used. Of poly {3- (4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoro- 1-undecyloxy) thiophene} (P1-3) 3.51 parts were obtained (25% overall yield).

<Production Example 4>
Synthesis of poly {3- (4,4,5,5,5-pentafluoro-2-oxapentyl) thiophene} (P1-4):
(1) Synthesis of 3-bromomethylthiophene;
3-methylthiophene [Tokyo Chemical Industry Co., Ltd.] 5 parts (50.9 mmol), N-bromosuccinimide 9.97 parts (56.0 mmol), dibenzoyl peroxide [Tokyo Chemical Industry Co., Ltd.] 0. After 12 parts (0.50 mmol) was dissolved in 30 parts of benzene, the temperature was raised to 100 ° C. and reacted for 4 hours. After completion of the reaction, the mixture was allowed to cool to room temperature, 30 parts of a 1M sodium thiosulfate aqueous solution was added and the mixture was transferred to a separatory funnel, and the aqueous layer was separated. Further, the organic layer was washed twice with 30 parts of distilled water, and then benzene was distilled off to obtain 6.32 parts (35.7 mmol) of 3-bromomethylthiophene (yield 70.1%).

(2) Synthesis of 3- (4,4,5,5,5-pentafluoro-2-oxapentyl) thiophene;
2.89 parts (39.3 mmol) of 2,2,3,3,3-pentafluoro-1-propanol was dissolved in 15 parts of THF, and 1.57 parts of sodium hydride (60% paraffin dispersion) (39. 3 mmol) was added. 6.32 parts (35.7 mmol) of 3-bromomethylthiophene was dissolved in 15 parts of THF and added dropwise over 2 hours, and then heated to 100 ° C. and reacted for 4 hours. After completion of the reaction, the reaction mixture was allowed to cool to room temperature, 30 parts of distilled water was added and the mixture was transferred to a separatory funnel, and the aqueous layer was separated. Further, the organic layer was washed twice with 30 parts of distilled water, THF was distilled off, and the resulting mixture was purified with a silica gel column to give 3- (4,4,5,5,5-pentafluoro-2. -7.47 parts (30.35 mmol) (oxapentyl) thiophene (yield 85%) were obtained.

(3) Synthesis of 2,5-dibromo-3- (4,4,5,5,5-pentafluoro-2-oxapentyl) thiophene;
3.47 parts (30.35 mmol) of 3- (4,4,5,5,5-pentafluoro-2-oxapentyl) thiophene and 11.07 parts (62.21 mmol) of N-bromosuccinimide in 30 parts of THF And reacted at room temperature for 2 hours.
The precipitate was removed with a glass filter using 50 parts of ethyl acetate, and THF and ethyl acetate were distilled off. The resulting mixture was purified with a silica gel column to obtain 9.44 parts (23.37 mmol) of 2,5-dibromo-3- (4,4,5,5,5-pentafluoro-2-oxapentyl) thiophene ( Yield 77%) was obtained.

(4) Synthesis of poly {3- (4,4,5,5,5-pentafluoro-2-oxapentyl) thiophene};
After dissolving 9.44 parts (23.37 mmol) of 2,5-dibromo-3- (4,4,5,5,5-pentafluoro-2-oxapentyl) thiophene in 30 parts of THF, methylmagnesium bromide 23.14 parts (23.37 mmol) of THF solution was added and reacted at 75 ° C. for 30 minutes. To the reaction solution, 0.127 part (0.234 mmol) of [1,3-bis (diphenylphosphino) propane] -dichloronickel (II) was added, and the reaction was further continued for 2 hours at 75 ° C. The reaction solution was allowed to cool to room temperature, and 5 parts of methanol was added. The reaction mixture was transferred to a Soxhlet extractor and washed sequentially with 150 parts of methanol, 150 parts of chloroform and 150 parts of acetone. Finally, the residue is extracted with 150 parts of 1-methyl-2-pyrrolidone, and the solvent is distilled off to obtain poly {3- (4,4,5,5,5-5-stereoregularity of 96.7%. 2.28 parts (pentafluoro-2-oxapentyl) thiophene} (P1-4) (yield 40%, total yield 18%) were obtained.

<Production Example 5>
Synthesis of poly {3- (4,4,5,5,6,6,6-heptafluoro-2-oxahexyl) thiophene} (P1-5):
2.86 parts of 2,2,3,3,4,4,4-heptafluoro-1-butanol instead of 5.89 parts of 2,2,3,3,3-pentafluoro-1-propanol [Tokyo Kasei Except for using Kogyo Co., Ltd.], 2.51 parts of (P1-5) having a stereoregularity of 97.4% were obtained in the same manner as in Production Example 4 (17% overall yield).

<Production Example 6>
Synthesis of poly {3- (5,5,6,6,7,7,8,8,8-nonafluoro-2-oxaoctyl) thiophene} (P1-6):
10.37 parts of 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexanol instead of 5.89 parts of 2,2,3,3,3-pentafluoro-1-propanol Was used in the same manner as in Production Example 4 to obtain 2.97 parts of (P1-6) having a stereoregularity of 95.9% (total yield: 16%).

<Production Example 7>
Synthesis of poly {3- (5,5,6,6,7,7,8,8,9,9,10,10,10-tridecafluoro-2-oxadecyl) thiophene} (P1-7):
Instead of 5.89 parts of 2,2,3,3,3-pentafluoro-1-propanol 3,3,4,4,5,5,6,6,7,7,8,8,8-tri 3.79 parts of (P1-7) having a stereoregularity of 95.8% were obtained in the same manner as in Production Example 4 except that 14.30 parts of decafluoro-1-octanol was used (total yield of 16 %).

<Production Example 8>
Synthesis of sulfonated poly {3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene} lithium salt (P2-1):
(1) Synthesis of sulfonated poly {3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene};
180 parts of fuming sulfuric acid was mixed with 2.95 parts of (P1-1) obtained in Production Example 1, and reacted at 85 ° C. for 24 hours. The reaction mixture was diluted with 6000 parts of distilled water and then stirred at room temperature for 1 hour to be dispersed. The dispersion was settled using a centrifuge, the supernatant was removed, and then washed twice with 800 parts of distilled water using a centrifuge. The obtained precipitate was put into 6000 parts of distilled water and dispersed by irradiating with ultrasonic waves for 30 minutes.
The obtained dispersion was passed through a column packed with 30 parts of an ion exchange resin (Amberjet 4400, manufactured by Aldrich). After removing residual sulfonic acid, water was distilled off under reduced pressure to obtain sulfonated poly {3- ( 4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene} 3.16 parts (yield 96%).

(2) Synthesis of sulfonated poly {3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene} lithium salt;
After 3.16 parts of the sulfonated poly {3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene} is dispersed in 50 parts of distilled water, 0.60 part of lithium carbonate was added and reacted at room temperature for 1 hour. The reaction mixture was depressurized to distill off water, and sulfonated poly {3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene} lithium salt (P2 -1) 3.19 parts (yield 99%, total yield 95%) were obtained.
The obtained sulfonated poly {3- (4,4,5,5,6,6,7,7,7-nonafluoro-1-heptyloxy) thiophene} lithium salt was analyzed by NMR. The content of (D1) was 49 mol%, and the content of the repeating unit (E1) of thiophene was 51 mol%.

<Production Example 9>
Synthesis of sulfonated poly {3- (4,4,5,5,5-pentafluoro-2-oxapentyl) thiophene} lithium salt (P2-2):
(P1-1) In the same manner as in Production Example 8, except that 2.28 parts of (P1-4) obtained in Production Example 4 were used instead of 2.95 parts, sulfonated poly {3- (2, 5-dioxapentylheptyl) thiophene} lithium salt (P2-2) 2.46 parts was obtained (91% overall yield). As a result of analyzing the obtained sulfonated poly {3- (4,4,5,5,5-pentafluoro-2-oxapentyl) thiophene} lithium salt by NMR, the content of the repeating unit (D4) of thiophene was The content of 52 mol% of thiophene repeating units (E4) was 48 mol%.

<Comparative Production Example 10>
Synthesis of poly (3-hexyloxythiophene) (P′-1):
3,3,4,4,5,5,6,6,6-nonafluoro-1-hexanol was used in the same manner as in Production Example 1 except that 15.65 parts of 1-hexanol was used instead of 15.92 parts. 2.85 parts of poly (3-hexyloxythiophene) (P′-1) having a stereoregularity of 96.7% was obtained (overall yield 30%).

<Comparative Production Example 11>
Synthesis of sulfonated poly (3-hexyloxythiophene) lithium salt (P′-2):
(P1-1) A sulfonated poly (3-hexyloxy) was prepared in the same manner as in Production Example 8 except that 2.85 parts of (P′-1) obtained in Production Example 10 was used instead of 2.95 parts. Thiobene) lithium salt (P'-2) 3.23 parts was obtained (91% overall yield). The obtained sulfonated poly (3-hexyloxythiophene) lithium salt was analyzed by NMR. As a result, the content of the repeating unit (F) of thiophene was 52 mol%, and the content of the repeating unit (E) of thiophene was 48 mol. %Met.

<Production Example 12>
Production of negative electrode:
92.5 parts of graphite powder having an average particle size of about 8 to 12 μm, 7.5 parts of polyvinylidene fluoride, and 200 parts of 1-methyl-2-pyrrolidone [manufactured by Tokyo Chemical Industry Co., Ltd.] are thoroughly mixed in a mortar to obtain a slurry. Obtained. The obtained slurry was applied to one side of a 20 μm thick copper foil, dried at 120 ° C. for 15 minutes to evaporate the solvent, punched out to 12 mmφ, and made a negative electrode with a thickness of 30 μm using a press.

<Production Example 13>
Preparation of lithium secondary battery electrolyte:
LiPF ₆ as an electrolyte was dissolved in a mixed solvent of ethylene carbonate: diethyl carbonate: vinylene carbonate = 48.5: 48.5: 3 (weight ratio) to prepare an electrolyte solution.

Examples 1-14 and Comparative Examples 1-5
<Preparation of additive>
The substituted polythiophene obtained in the above Production Examples 1 to 11, the polyvinylidene fluoride as a binding force assisting polymer compound, carboxymethyl cellulose and polyaniline sulfonic acid were mixed in the weight ratios shown in Tables 1 and 2, and Examples Additives for 1-14 and Comparative Examples 1-5 were prepared.

<Preparation of positive electrode>
0.25 parts of additives for Examples 1 to 10, 13, 14 and Comparative Examples 1, 2, 4 and 5, 9.5 parts of LiFePO ₄ powder, acetylene black as a conductive assistant (manufactured by Denki Kagaku Kogyo Co., Ltd.) , 0.25 part of average particle diameter: 1.0 μm) and 7.0 part of 1-methyl-2-pyrrolidone [manufactured by Tokyo Chemical Industry Co., Ltd.] were sufficiently kneaded in a mortar. 13, 14 and Comparative Examples 1, 2, 4, and 5 were obtained.
The obtained slurry was applied to one side of an aluminum electrolytic foil current collector having a thickness of 20 μm using a wire coating bar in the air, dried at 100 ° C. for 15 minutes, and further subjected to 80 ° C. under reduced pressure (10 mmHg). Drying was performed at a temperature of 5 ° C. for 5 minutes to form a layer made of an active material and an additive having a thickness of 10 μm on the aluminum electrolytic night, and a positive electrode having a total film thickness of 30 μm was produced.
Further, 0.25 parts of additives for Examples 11 and 12 and Comparative Example 3, 9.5 parts of LiFePO ₄ powder, acetylene black as a conductive assistant (manufactured by Denki Kagaku Kogyo Co., Ltd., average particle size: 1.0 μm) ) 0.25 part and 7.0 parts of water were sufficiently kneaded in a mortar to obtain slurries for Examples 11 and 12 and Comparative Example 3, respectively.
The obtained slurry was applied to one side of an aluminum electrolytic foil current collector having a thickness of 20 μm using a wire coating bar in the air, dried at 100 ° C. for 15 minutes, and further subjected to 80 ° C. under reduced pressure (10 mmHg). Drying was performed at a temperature of 5 ° C. for 5 minutes to form a layer made of an active material and an additive having a thickness of 10 μm on the aluminum electrolytic night, and a positive electrode having a total film thickness of 30 μm was produced.

<Preparation of secondary battery evaluation cell>
A secondary battery cell in which the positive electrodes for Examples 1 to 14 and Comparative Examples 1 to 5 and the negative electrode obtained in Production Example 12 are arranged at both ends in a 2032 type coin cell so that the coated surfaces face each other. Was made. The electrolyte solution prepared in Production Example 13 was injected into the cell to obtain an evaluation cell.

[Evaluation]
Using the obtained additive, positive electrode, and evaluation cell, the following evaluation methods were used for binding strength, dispersibility in polyvinylidene fluoride, withstand voltage, battery output, capacity retention rate, capacity retention during high-speed charge / discharge. Tables 1 and 2 show the evaluation results of the rate and the cycle characteristic deterioration rate during high-speed charge / discharge.

<Evaluation of binding power>
According to the cross cut test method JIS K5400, the surface of the positive electrode film is scratched in a 10 × 10 square cross cut, and a cellophane adhesive tape (manufactured by Nichiban Co., Ltd.) is pasted and peeled off, and then the positive electrode mixture The number of squares remaining in the layer is visually counted, and the binding force is calculated from the following formula.
Binding power (%) = (Number of remaining squares / 100) × 100

<Evaluation of dispersibility of substituted polythiophene (P) in polyvinylidene fluoride>
A slurry obtained by sufficiently kneading 1.0 part of an additive and 7.0 parts of 1-methyl-2-pyrrolidone [manufactured by Tokyo Chemical Industry Co., Ltd.] in a mortar is applied to an aluminum foil, and in the atmosphere. After drying at 100 ° C. for 15 minutes, the sample was further dried under reduced pressure (1.5 kPa) at 80 ° C. for 5 minutes to prepare a test sample. The substituted polythiophene (P) in the prepared test sample was vapor-phase dyed with ruthenium tetroxide, and in polyvinylidene fluoride using a transmission electron microscope (TEM) "H-7100 type manufactured by Hitachi, Ltd." The dispersed particle size (nm) of the substituted polythiophene (P) was measured. However, the additives of Examples 11 and 12 and Comparative Example 3 are not measured because they do not dissolve in polyvinylidene fluoride. Moreover, since the additive of the comparative examples 4 and 5 does not contain substituted polythiophene, it has not measured.

<Evaluation of withstand voltage>
An electrode obtained by applying 5 mg of substituted polythiophene (P) to an aluminum foil is a working electrode, a lithium foil is a counter electrode and a reference electrode, and an electrolytic solution is mixed at a ratio of ethylene carbonate: diethyl carbonate = 50: 50 (volume ratio). Using a tripolar cell in which lithium hexafluorophosphate was dissolved in a solvent at a rate of 1 mol / L, a potentiostat / galvanostat (manufactured by Bio Logic) at 65 ° C., 3.0-5 Cyclic voltammetry (CV) is performed at a voltage range of 0.0 V and a sweep speed of 1 mV / sec to determine the Coulomb efficiency of the substituted polythiophene (P). The higher the value of Coulomb efficiency, the better the withstand voltage performance.

<Evaluation of battery output>
Using a charge / discharge measurement device “Battery Analyzer 1470” [manufactured by Toyo Technica Co., Ltd.], charge so that SOC (State of charge, the ratio of the capacity in a fully charged state to the capacity at a predetermined time) is 60%. Then, discharge at a constant current and read the voltage after 10 seconds. This operation is performed with several current values, and the current value on the horizontal axis and the voltage value after 10 seconds are plotted on the vertical axis to create an approximate line, and the current value (I ₃ when the approximate line intersects with 3V) _.0V ) and battery output is calculated from the following formula.
Battery output (W) = I _3.0V x 3.0

<Evaluation of capacity retention>
And a charge-discharge measuring instrument was used "Battery Analyzer 1470 model", was charged from the voltage 0V by the current 0.2 mA / cm ² until 2V, after 10 minutes of resting, the battery voltage of the current 0.2 mA / cm ² 0V This charge / discharge is repeated 50 cycles.
At this time, the battery capacity at the first charge and the battery capacity at the 50th cycle charge are measured, and the capacity retention rate is calculated from the following formula. It shows that charging / discharging cycling characteristics are so favorable that a numerical value is large.
Capacity retention rate (%) = (battery capacity at the 50th cycle charge / battery capacity at the first charge) × 100

<Evaluation of capacity retention during high-speed charge / discharge>
And a charge-discharge measuring instrument was used "Battery Analyzer 1470 model", was charged from the voltage 0V by the current 0.5 mA / cm ² until 2V, after 10 minutes of resting, the battery voltage of the current 0.5 mA / cm ² 0V The battery is discharged until this charge / discharge is repeated.
At this time, the battery capacity at the first charge and the battery capacity at the 50th cycle charge are measured, and the capacity retention rate at the high speed charge / discharge is calculated from the following formula. It shows that a high-speed charge / discharge cycle characteristic is so favorable that a numerical value is large.
Fast charge / discharge capacity retention ratio (%) = (battery capacity at the 50th cycle charge / battery capacity at the first charge) × 100

<Evaluation of cycle characteristics deterioration rate during high-speed charge / discharge>
The cycle characteristic deterioration rate during high-speed charge / discharge is calculated based on the following formula. The larger the value, the better the cycle characteristics during high-speed charge / discharge compared with the normal charge / discharge.
Cycle characteristic deterioration rate during high-speed charge / discharge (%) = (high-speed charge / discharge capacity retention ratio / capacity retention ratio) × 100

From Tables 1 and 2, it can be seen that the additive of Example 1 has a larger battery output and superior output characteristics than the additive of Comparative Example 1, and also has good cycle characteristics even during high-speed charge / discharge.
It can be seen that the additives of Examples 4 to 10, 13 and 14 have larger battery output and superior output characteristics than the additive of Comparative Example 2, and also have good cycle characteristics even during high-speed charge / discharge.
Moreover, when the polyvinylidene fluoride in the positive electrode additive was used, the additives of Examples 4 to 10, 13 and 14 were substituted with the substituted polythiophene (P) in the polyvinylidene fluoride from the binder of Comparative Example 2. It can be seen that the dispersibility of
It can be seen that the additives of Examples 11 and 12 have larger battery output and better output characteristics than the additive of Comparative Example 3, and also have good cycle characteristics even during high-speed charge / discharge.
The additive for positive electrode of the present invention can sufficiently withstand the binding force of the coating film applied to the aluminum electrolytic foil surface, and the positive electrode produced using these positive electrode additives has excellent output characteristics, and It can be seen that the cycle characteristics are good even during high-speed charge / discharge.

  Since the additive for positive electrodes of the lithium secondary battery of the present invention is excellent in electronic conductivity and ion conductivity, it is also useful as an additive for batteries other than lithium secondary batteries. Moreover, since the lithium secondary battery using the additive of the present invention is excellent in output and safety, it is useful for electric vehicles.

Claims (10)

At least one group (f) selected from the group consisting of groups (f1) to (f4) in which the hydrogen atoms at the 3-position and / or 4-position of the thiophene ring are respectively represented by the following general formulas (1) to (4) An additive for a lithium secondary battery positive electrode comprising, as an essential component, a substituted polythiophene (P) having the repeating unit (D) substituted with at least a part of the thiophene repeating units.
—OR ¹ —R ² (1)
[Wherein, R ¹ represents an alkylene group having 1 to 6 carbon atoms, and R ² represents a perfluoroalkyl group having 1 to 15 carbon atoms. ]
—O—R ³ (2)
[Wherein R ³ represents a perfluoroalkyl group having 1 to 15 carbon atoms. ]
—R ⁴ —O—R ⁵ (3)
[Wherein, R ⁴ represents a linear or branched alkylene group having 1 to 6 carbon atoms, and R ⁵ represents a perfluoroalkyl group having 1 to 15 carbon atoms. ]
—R ⁶ —OR ⁷ —R ⁸ (4)
[Wherein R ⁶ represents a linear or branched alkylene group having 1 to 6 carbon atoms, R ⁷ represents an alkylene group having 1 to 6 carbon atoms, and R ⁸ represents a perfluoroalkyl group having 1 to 15 carbon atoms. Represents. ] The repeating unit (D) is at least one repeating unit selected from the group consisting of repeating units (D1) to (D4) respectively represented by the following general formulas (5) to (8). Additive.

  The repeating unit (D) is 2,2,2-trifluoroethoxy group, 2,2,3,3,3-pentafluoropropoxy group, 2,2,3,3,4,4,4-heptafluorobutoxy Group, 2,2,3,3,4,4,5,5,5-nonafluoropentoxy group, 3,3,3-trifluoro-1-propoxy group, 4,4,4-trifluoro-1 The additive according to claim 1 or 2, which is a repeating unit substituted with at least one group selected from the group consisting of -butoxy group and 5,5,5-trifluoro-1-pentoxy group.   The additive according to any one of claims 1 to 3, wherein the content of the repeating unit (D) is 50 to 100 mol% based on the weight of the substituted polythiophene (P). The group (g) represented by the following general formula (9) is bonded to the 3-position or 4-position of one or more thiophene rings in the substituted polythiophene (P). Additives.
-SO ₃ ^- M ⁺ (9)
[Wherein M ⁺ represents an alkali metal cation or a proton. ]   The additive according to any one of claims 1 to 5, wherein the stereoregularity defined by the percentage of the head-to-tail-head-to-tail bond of the substituted polythiophene (P) is 90% or more.   Furthermore, the additive of any one of Claims 1-6 containing a polyvinylidene fluoride and / or polytetrafluoroethylene.   Furthermore, the additive of any one of Claims 1-6 containing a carboxymethylcellulose.   The positive electrode for lithium secondary batteries containing the additive of any one of Claims 1-8, an active material (B), and a collector (C).   The lithium secondary battery using the positive electrode containing the additive of any one of Claims 1-8.